What Is MK-677?
MK-677 (Ibutamoren) is a potent, orally active, non-peptide GH secretagogue — a ghrelin receptor (GHSR-1a) agonist that mimics ghrelin's ability to stimulate pituitary GH release. Developed by Merck, it was the first orally bioavailable GH secretagogue to enter clinical trials. Unlike all other GH secretagogues (which are peptides requiring injection), MK-677 survives oral administration intact and produces sustained elevations in both GH and IGF-1 over a 24-hour period from a single daily dose.
Mechanism and Pharmacokinetics
MK-677 activates GHSR-1a on pituitary somatotrophs with high affinity and selectivity. Its non-peptide structure allows oral bioavailability of approximately 60–70%, and its 4–6 hour half-life produces a sustained GH secretory response that maintains IGF-1 elevation throughout the day — a 24-hour profile that distinguishes it from injectable GH secretagogues whose effects are more pulsatile.
Clinical Research Findings
Clinical trials in healthy elderly adults demonstrated significant increases in GH and IGF-1 levels (to young adult ranges), improved body composition (increased lean mass, decreased fat mass), improved sleep quality (particularly slow-wave sleep), and normalized bone turnover markers. A 2-year trial showed sustained GH/IGF-1 elevation and lean mass preservation without significant adverse effects beyond mild fluid retention at higher doses.
Quick Reference
Member reference tables summarize the compound's research parameters.
Research Indications
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below), not a personal dosing recommendation.
This member section describes parameters reported in the research literature.
Peptide Interactions
This member section summarizes reported compound interactions and evidence limitations.
Reported Research Time Points
This member section summarizes reported research time points.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
This member section discusses research safety considerations and uncertainties.
Quality Indicators
Research Citations
- Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects
Chapman, I.M., Bach, M.A., Van Cauter, E., et al., 1996, Journal of Clinical Endocrinology & Metabolism - MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism
Murphy, M.G., Plunket, L.M., Gertz, B.J., et al., 1998, Journal of Clinical Endocrinology & Metabolism - Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure
Svensson, J., Lönn, L., Jansson, J.O., et al., 1998, Journal of Clinical Endocrinology & Metabolism - Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man
Copinschi, G., Leproult, R., Van Onderbergen, A., et al., 1997, Neuroendocrinology - LGD-4033 and MK-677 use impacts body composition, circulating biomarkers, and skeletal muscle androgenic hormone and receptor content: A case report
Cardaci, T.D., Machek, S.B., Wilburn, D.T., et al., 2022, Experimental Physiology - Structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren
Liu, H., Kim, H.R., Deepak, R.N.V.K., et al., 2021, Nature Communications - Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial
Nass, R., Pezzoli, S.S., Oliveri, M.C., et al., 2008, Annals of Internal Medicine - MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study
Adunsky, A., Chandrasekaran, K., Wind, S., et al., 2011, Archives of Gerontology and Geriatrics - A Study of the Metabolism of Ibutamoren (MK-677), a Growth Hormone Secretagogue, in Human Urine by Ultra-High-Performance Liquid Chromatography–High-Resolution Mass Spectrometry
Dmitrieva, E.V., Anikina, L.V., Ostroukhova, T.V., et al., 2024, Journal of Analytical Chemistry - Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats
Lee, J., Park, S., Lim, A., et al., 2018, Yonsei Medical Journal - MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism
Murphy MG, Plunkett LM, Gertz BJ, 1998, J Clin Endocrinol Metab - Oral administration of growth hormone (GH) releasing peptide-mimetic MK-677 stimulates the GH/insulin-like growth factor-I axis in selected GH-deficient adults
Chapman IM, Pescovitz OH, Murphy G, 1997, J Clin Endocrinol Metab - Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. The MK-677 Study Group
Murphy MG, Bach MA, Plotkin D, 1999, J Bone Miner Res - Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats
Lee J, Kwon A, Chae HW, 2018, Yonsei Med J - Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women
Murphy MG, Weiss S, McClung M, 2001, J Clin Endocrinol Metab